Bird Island Cape gannets make a comeback with help from their friends

A breeding pair in conversation. (Photo: Zanri Strydom)

30 Jan 2025

Cape gannets, endemic to southern Africa, were on the decline, but intensive protection at Lambert’s Bay has led to a brilliant turnaround.

Whatever twists an Olympic diver does in the air, by the time she hits the water her position is always with hands held in a point to break the water and head tucked between her arms. It is quite likely that humans learnt to dive this way from watching aquatic birds. Our Olympic diver could find no better teacher than a Cape gannet.

As pelagic hunters, they’re masters of the dive. With streamlined bodies and tapered wings, they can plunge from heights of 30m at speeds of more than 100km/h, slicing the water surface with hardly a splash.

https://youtu.be/aFupBT2heoc?si=0wKOkhl4CcvAyq09

Endemic to southern Africa, gannets have faced some tough challenges over the years, from dwindling fish stocks to persistent predators and habitat disruptions. Between 1956 and 2015 their global population dropped by half, largely from trawlers stealing their food and warming oceans that pushed prey further offshore. Lambert’s Bay, one of only three Cape Gannet colonies left in South Africa, was not spared these pressures.

But here’s good news: the population at Lambert’s Bay Bird Island is bouncing back.

In January 2025, the colony hit a milestone of 45,000 individuals – the highest number in nearly 20 years. This marked a significant increase for the island, with numbers consistently remaining in the 30,000s over the past five years.

“The island offers the perfect conditions for the birds to thrive,” says CapeNature. “With enough space, minimal predation, access to food and consistent conservation efforts, this makes it ideal for gannets seeking a safe home to raise their young.”

The significant growth of the colony is not just a product of local breeding success on the island. It also suggests that gannets from other colonies are flocking to Bird Island, recognising it as a prime breeding ground.

A panoramic view of 45,000 gannets at Bird Island. (Photo: CapeNature)

Gannets A gannet breeding colony. (Photo: CapeNature)

The protectors

Mostly, though, the success story is thanks to dedicated conservation work, smart management and unwavering commitment by scientists and CapeNature to protecting these beautiful birds.

Predation is a serious threat to gannets, particularly during chick fledging season. Without proper control, seals could completely take over the island and overwhelm the colony, resulting in temporary or permanent abandonment of the site by the gannets.

To prevent this, an invisible barrier line was put in place, restricting the seals to a specific area on the western side of the island. If they cross this boundary, they’re herded back to their designated zone. This has proved highly effective in preventing them from encroaching on the gannets’ space.

Kelp gulls are also always on the lookout for an easy meal, targeting gannet eggs and chicks, especially those on the edges of the nesting area. Efforts to manage gulls have had some success, although new gulls often replace those that get removed.

Doctoral research by Zanri Strydom – a reserve manager of Dunefields Private Nature Reserve near George – found that carefully managed culling of problematic seals during key times helped reduce fledgling losses. GPS trackers and accelerometers have disclosed fascinating details about gannet foraging habits.

Zanri Strydom at work with an attentive audience. (Photo: CapeNature)

Part of the 45,000 gannet colony at Bird Island. (Photo: CapeNature)

One of the findings is that older gannets, despite their experience, often use up more energy than younger ones because of age-related physical decline. This highlights the importance of having a mix of ages in the colony to keep it resilient.

Where gannets choose to nest also matters a lot. Nests at the centre of the colony, Strydom discovered, are less vulnerable to predators compared with those on the edges. This kind of insight helps conservationists tweak strategies to give the birds a better shot at raising their chicks successfully.

The Bird Island comeback has required intensive teamwork. Each day a dedicated team patrols the colony, keeping an eye out for threats, making sure the ecosystem stays in balance and discouraging human disturbances.

CapeNature has worked with local communities, fishers and conservation groups to create a supportive environment for the birds. And because Bird Island is uniquely accessible – you can actually walk to it – the sanctuary has become a hub for ecotourism and education. Visitors leave with a deeper appreciation for these birds and the vital work being done to protect them.

“Bird Island’s success is a valuable example of the effectiveness of hands-on conservation,” said Dr Ashley Naidoo, CEO of CapeNature. “Through constant monitoring, proactive management of threats like seals and gulls, and a commitment to conserving the island’s unique ecosystem, Bird Island can claim to be the best-managed gannet colony in southern Africa.”

A Cape gannet. (Photo: CapeNature)

A breeding pair in conversation. (Photo: Zanri Strydom)

Local and special

Cape Gannets are endemic to southern Africa, with their breeding confined to six islands: Mercury, Ichaboe and Possession islands off Namibia and, off South Africa, Lambert’s Bay Bird Island, Malgas Island and Bird Island in Algoa Bay. All of these are in the west coast’s food-rich Benguela cold-water upwelling system. After the breeding season they disperse along the coastlines, ranging from as far as the Gulf of Guinea on Africa’s west coast to Mozambique on the east, typically staying within 100km of the shore.

In 2015, their global population was estimated at about 123,000 breeding pairs but there’s been a significant shift in their distribution over the past decades. In the late 1950s, about 80% of the population bred on Namibian islands, but by 2015 this figure had declined to about 5%, with most now breeding in South Africa.

Their numbers have fluctuated over time for various reasons, including changes in the availability of fish and environmental conditions. It was the collapse of sardine stocks in Namibia from overfishing that led to a massive decline there.

“The success of the operations on Bird Island shows what can be achieved through sustained dedication and management techniques,” says CapeNature. “With the colony now thriving, Bird Island stands as an example for the future of gannet conservation and the broader health of southern Africa’s coastal ecosystems.” DM

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The protectors

Local and special